were they sold to you as a sexed pair? they look a little small to be sexed 100%, the head bobbing is a more typically male trait, and arm waiving if more female, but not always, i had one i thought was a male forever and had living with a female, acted more male, but latter looked and surprise, it was a girl!
were you going to try to breed? if they are just pets, 2 girls would get along just as well for the most part, males may fight so lookout for that.
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hanging out under heat lights burns up my brain cells!!